Testing instrument



wQBRoAD TESTING INSTRUMENT FiledV June 5, 1924 March 1 y Patented Mar. 1, 1927.

iunit-15in stares 1 rarest orric-E..

WILLIAM BROAD, QF BEAVER FALLS, PENNSYLVANIA, ASSIGNOROF TI-IREE-FOURTHS T0 H. E. MCLAIN, OF "EITTS'BRGH, PENNSYLVANIA.

'rns'rme- INSTRUMENT.

Appncaiion' mea :une 5, 1924.- seriai no'. 718,006.

The present invention relates broadly to testing instruments, and more particularly to al miniature `millivolttesting battery for high resistance circuits, or circuits containing delicate instruments to which the application of an appreciable voltageI` or current might prove disastrous.

Great diiliculty is sometimes encountered inthe testing of high resistance circuits due to inability to produce a current flow su'liicient to give an indication ot the condition oit the circuit being tested.. I 'have found that with a voltaic cell constructed in accordance with the present invention, and operating to produce only a .small fraction of a volt it is possible to give an effective indication through circuits having resistances well in excess of 50,000 ohms.

The increasing use ot radio receiving and transmitting sets utilizing extremely delicate instruments offers another iield for a small millivolt testing battery which may be easily and inexpensively procured and operated.

In certain cases,-`as for example in mines,

' powder plants andi the like, where explosive gases or materials are present, it is trequently necessary to make tests :tor circuits on diiterent pieces ot electrical equipment. In Ksuch cases, it isessential that the testing instruments be so constructedas to prevent the possibility or" a spark capable ot producing an explosion.

The present invention has for its object the production ot a testingbattery meeting the requirement-s referred to, and ot such construction that it may be operated over a period ot' years without appreciable deterioration, the actual deterioration depending upon the actual length ot time the battery is in active service.

In the accompanying drawings, there are shown tor purposes ot illustration only certain preferred embodiments of the present invention, it being understood that the drawings do not define the limits of lmy invention as changes in the construction and operationdisclosed therein may be made Without `departing from the spirit ot the invention or the scope ot my broader claims.

In the drawings Figure 1 is a vertical sectional view, certain ot the parts being shown in elevation, of one form of testing battery embodying` the present invention;

Figure 2 is a detail View, partly Figure 3 is a. view similar tofFigure l.

Villustrating a slightly modied embodiment ot' the invention;

Figure 4 `is a detail sectional view on an enlarged scale on the .li-ne -IV---IV off Figure; i

Figure 5 is a diagrammatic view illustrating one form ot testing circuit; andV Figure 6 is a view similar `to Figure l' illustrating still another embodiment of the present invention. i

I'Thile in accordance with-the present invention the actual size of the battery is relatively immaterial, it e may be Vstated that for General purposes the battery is very smali,`it being in fact much smaller than indicated in any of the drawings with the possible exception of Figure 5, inwliich it is shown in' substantially full size. 'As will be apparent from the claims, however, the invention is not limitedin this respect, it merely being possible, by-reasonof lthe construction illustrated, to` make an extremely small and Acompact lbattery Y.which may be inexpensively manufactured and sold accordingly. v

In the embodiment illustrated in Figure 1, there is provided a casing'Q, constituted bya conductor of the lirst class such as zinc. The casing as initially formed is preferably ot truly cylindricalV shape having a constant internal diameter. liVithin the casing, `there isk inserted a second conductor of the iirst class .conveniently comprising a length oit' copper bent in the form ot a spring 3. Intermediate .the two conductors oft the iirst class is an absorbent material such as a-plu- 'rality 4oft layers ot paper 4. After the spring 3 and the absorbent material "have been inserted into the casing, fiber disks 5 are preferablyplaced in the ends thereof, andthe endslthereupon bent or spun inwardly to ei'lect-ively hold the 'parts in position. v

In accordance with the preferred embodinient` ot the presentinvention, the spring 3 will preterably have a normal length i slightly inexcess ot the length ot the casing, whereby when the ends 6" are bent inwardly, the coils otl thespring will be held under compression. This exerts an outward pressure on the disks 5- tending to hold the parts firmly in position. Each of the disks 6 preferably has a` central opening 7 adapted not only to permit the application of desired quantity of a conductor of the second class, but alsoV permitting connection to be established With the inner conductor. Adapted to tightly engage' either end of the casing is a cap 8 preferably of the same material as that of which the casing is constructed, and having projecting therefrom a tip or connection 9 of suitable material. 7When it is'desired to place the battery in operation, the cap S is removed and a very small quantity of a suitable electrolyte, constituting al conductor of the second class, is applied to the opening 7 in one ofthe disks. The desired results may easily be obtained by simply moistening the disk with the end of one of the lingers. The cap is thereafter applied, and a connee-tion 10 slipped through the other opening 7 into Contact With the sprinO. Upon connecting the ends of the circuit to be tested with the tips 9 and 10, respectively, and including Within the circuit a suitable indicating instrument, such as a sensitive telephone receiver, there Will be produced a minute current ioW which Will give an audible signal in the receiver. By repeatedly opening and closing the circuit, a series of such signals Will be given. In actual practice, it has been found that a voltaic cell of theconstruction described vhas the ability to give a signal of this character through 'a circuit of extremely high resistance Without any possibility of producing a spark, and'without the generation of current to an extent suiiicient to injure even the most sensitive instrument.

ln Figures 3 and t, there is illustrated a slightly modified embodiment of the invention, in which parts corresponding to parts already described are designated by the same reference characters having a prime aiiixed thereto. In this form of the invention, the tip 10 is connected to a chuck 11 comprising spring fingers having inclined outer ends 12 adapted to be engaged by a cap13 and forced inwardly into engagew ment with a wire 14: or the like with Which it is desired to make connection. The tip 10 may either be loosely inserted, or may be soldered Within the coil as may be desired. lt will be apparent that the provision of a chuck ll'makes it possible to establish eflicient connection with conductors of different sizes.

In Figure 5, there is illustrated a cell of the'character shown more particularly in Figure 3 in series with a resistance C indicating the circuit to be tested and a receiver R indicating diagrammatically the testing instrument employed.

ln the form of the invention illustrated in Figure G, the entire structure is shown as enclosed Within a protective casing 15. This casing may be of anydesired material, either metallic or nonaneta-llic, although preferably due to the ease of Working, l employ brass iny actual practice. In assembling the cell, the casing is first formed with a slightiy inturned end 16. A fiber Washer 7 is then placed Within the casing against the inturned flange. There is then slipped into the casing a Zinc cartridge containing therein an absorbent material 18 and a copper spring 19. The absorbent material and the spring may be held in position Within the zinc cartridger by a Washer 20 engaged by the inturned end 21 of the zinc. Thereafter, lthe end of the casing V15' is turned inwardly as indicated at 22 to hold all of the parts firmly in position.

rihe use of a protective casing not only shields the conductors utilized, but also makes it possible to assemble the trvo conductors ot' the first class in different relationships.

ln actual use, the amount of electrolyte applied Will be determined upon the length of time Which itis desired to maintain the cell in operation. An extremely small drop of electrolyte applied as herein described is sufficient to maintain the cell in operation for several hours., By thus limiting the quantity oi electrolyte, the chemical action on the Zinc may be reduced to a minimum u'fherebyY the length of life of the cell is materially increased, there lbeing no deterioration unless the cell is in actual use.

The smallv sizes in which the cell may be constructed permits it to be easily carried and permits it to be effectively used on any desired type ot circuit requiring testing Without fear of injury thereto or of the production ot' a spark.

Further advantages of the present invention arise from the construction of the cell whereby a circuit may be easily completed as may be desired.

I claim 1. ln a voltaic cell, a conductor of the first class forming a easing, a second conductor of the first class therein, and an absorbent -material between said conductors maintainductors, said casing being constructed 'to permit entry into said casing'to establish detachable contact with` said second-inentioned conductor and to permit the addition of the desired quantity of an electrolyte, substantially as described.

3. In a voltaic cell, a conductor of the first class forming a casing, a second conductor of the first class therein, an absorbent material between said conductors, said casing being constructed to permit entry thereinto to establish at will detachable contact with said second-mentioned conductor and to permit the addition of the desired quantity of an electrolyte, and a removable cover for said easing, substantially as described.

d. In a voltaic cell, a conductor voit the first class forming a. casing, a second conductor of the first class therein, an absorbent material between said conductors, said casing being constructed to permit contact with said second-mentioned conductor and to permit the addition of the desired quantity of an electrolyte, a removable cover 'for one end of said casing, and a removable conductor engaging means 'for the other end of said cell said cover and said means being interchangeably applicable at will to either end of said casing, substantially as described.

5. A testing instrument, comprising a casing of one metal, a coil spring of another metal therein, absorbent material between the different metals, and insulating disks at the ends of the casing, said casing being constructed to hold said disks in position with the spring under compression, and said disks being constructed to permit the addition of an electrolyte, at least one of said disks having' an opening therethrough substantially the diameter of the opening through said coil spring to facilitate de- `tachable frictional engagement with the inside of said spring, scribed.

substantially as de- 6. A testing instrument, comprising' a casi ing of one metal, a coil spring of another metal therein, absorbent material between the different metals, and insulatingl disks at the ends of the casing, said casing being constructed to hold said disks in position, and said disks being constructed to permit the addition of an electrolyte, at least one of said disks having an opening therethrough substantially the diameter of the opening through said coil spring to facilitate detachable trictional engagement with the inside of said spring, substantially as described.

7. A testing instrument, comprising a casing of one metal, a coil spring of another nietal therein, absorbent material between the different metals, insulating disks at the ends of the casing, said casing being constructed to hold said disks in position with the spring under compression, said disks being constructed to permit the addition of an electrolyte, and a removable cap for one end of said casing, at least one of said disks having an opening therethrough substantially'the diameter of the opening through said'coil spring to facilitate detachable Yfrictional Vengagement with the inside of said spring, substantially as described.

8. In a voltaic cell, a pair of conductors y tact with said casing, substantially as described.

l0. In a voltaic cell, a casing having inturned ends, disks ot' insulating material held in position by said ends, and a coil between said disks and normally `urging the disks outwardly, said coil disks and casing having aligned openings ior the reception of a conductor of the first class to establish contact with said coil, substantially as described. v

11. In a voltaic cell, a casing providing at least one arial opening and an open coil of metal within said casing having an axial opening in alignment with said first mentioned axial opening and oi substantially the same diameter as said first mentioned opening.

l2. In a voltaic cell, a casing providing at least one axial opening an open coil of metal within said casing having an' axial opening in alignment with said first mentioned axial opening and of substantially the same diameter as said first mentioned opening, and means normally maintaining said coil out of contact with said casing.

In testimony whereof l have hereunto'i set my hand.

VILLIAM BROAD. 

